For centuries, humans have been domesticating and breeding organisms to solve human problems and to improve their quality of life. Since the advent of molecular biology, genetic engineering has become the preferred route to improve microbial traits. In contrast to breeding, genetic engineering has focused largely on isolated pathways or regulatory circuits without considering the organism as a whole. Not surprisingly, the genetic redirection often falls short in meeting its full potential when the manipulated pathway is considered in vacuuo.
Many microorganisms have unique abilities to utilize renewable energy sources, such as cellulose, one of the most abundant renewable resources available. Other microorganisms are able to synthesize useful products, such as various hydrocarbons using simple sugar sources, such as those resulting from cellulose digestion. Unfortunately, the genetics and biochemistry of such microorganisms are not as well-known as compared to other genetically tractable model microbes, such as E. coli or Bacillus subtilis. In addition, the cultivation conditions for such microorganisms are frequently difficult or uneconomical to provide, thus hindering the use of these potentially useful microorganisms.
Thus there is a need to engineer microorganisms that make useful products from inexpensive renewable carbon sources. This requires the combination of traits from different organisms into one organism that can be industrially exploited.